A prior art piezoelectric filter structure is described in U.S. Pat. No. 4,427,913, issued Jan. 24, 1984 to Iafrate et al. The prior art piezoelectric filter structure includes a substrate of bulk gallium arsenide and two supported epitaxially grown layered structures, one layered structure on each side of the substrate, each layered structure having an epitaxially grown first layer of AlGaAs (aluminum gallium arsenide) and an epitaxially grown second layer of GaAs (gallium arsenide) and an epitaxially grown third layer of AlGaAs, and epitaxially grown fourth layer of GaAs, and the filter structure includes electrical transducer means mounted on each epitaxially grown fourth layer of GaAs.
One problem with the prior art structures is that it requires free major surfaces, which are difficult to make in a microresonator.
Another problem with the prior art structure is that, without the transducer means mounted on the outer layers, it cannot use (100) GaAs material, which is a principal material used in MMIC circuits.
One object of the present invention is to provide a resonator structure for a MMIC circuit which does not require free major surfaces.
Another object of the invention is to use the (100) GaAs material in a resonator structure which does not require external transducers means and matches this same material that is used in a MMIC circuit.